US2696979A - Automatic tuyere punching apparatus - Google Patents

Description

Dec. 14, 1954 B. T. BERGE 2,696,979

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Filed April 16, 1951 Dec. 14, 1954 a. T. BERGE 2,696,979

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United States Patent AUTOMATIC TUYERE PUNCHING APPARATUS Byron T. Berge, McGill, Nev., assignor to Kennecott Copper Corporation, New York, N. Y., a corporation of New York Application April 16, 1951, Serial No. 221,253

11 Claims. (Cl. 266-42) This invention relates to apparatus for mechanically punching the tuyeres of converters, and more particularly to automatically controlled fluid pressure operated apparatus for cleaning such tuyeres to remove encrustations or obstructions that are formed at the inner ends -of the tuyeres during blowing periods in which air is introduced through the tuyeres into the molten material under treatment in the converter.

Examples of fluid operated mechanical tuyere punching apparatus are shown in Larson and Berge Patent No. 2,432,996, issued December 23, 1947, and reference is made thereto for a further description of the operation of converters such as those used in the production of blister copper, and the necessity for frequent punching of the tuyeres to remove the obstructions and thereby maintain a satisfactory rate of introduction of blowing air. As brought out in said patent, it is advantageous to provide a separate complete punching unit mounted on the converter adjacent each tuyere and provided with motor means for effecting a rapid reciprocation of a punch rod within the tuyere, to move the tip of the punch rod rapidly inward past the zone of obstruction at the inner end of the tuyere and to then quickly reverse the movement and move the punch rod tip outwardly past the obstruction zone to a normal rest position within the tuyre.

Reference is also made to an application of Larson and Berge Ser. No. 109,084, filed August 8, 1949, now Patent No. 2,619,938, granted Dec. 2, 1952 which discloses a particularly advantageous type of fluid pressure operated motor for use in such a converter punching unit, in which an inward or forward stroke of the punch rod is effected by supply of motive fluid under pressure at the rearward side of a piston connected to the punch rod, and in which air is trapped and compressed forwardly ofthe piston during the forward stroke and is utilized to effect a rapid reversal and return stroke of the piston and punch rod.

In the forms of apparatus shown in the above mentioned patents, the operation of each punching unit to effect rapid reciprocatory movement of its punch rod is initiated by manual control means at such intervals as considered necessary in order to maintain a satisfactory rate of introduction of blowing air. The blowing air is normally supplied under suitable pressure through a manifold or bustle pipe having separate branch connections to the individual tuyeres, so that any excessive obstruction formed at the inner end of one or more individual tuyeres causes a material reduction in the rate of inflow of air through such tuyere or tuyeres. For optimum operation, it is desirable to maintain a relatively uniform high rate of introduction of air through all the tuyeres. More particularly, it is desirable to clean each individual tuyere promptly whenever it becomes so obstructed as to reduce the air flow therethrough below a certain minimum rate, and the principal object of this invention is to provide an automatically controlled apparatus for accomplishing this desirable result.

It accordingly becomes a particular object of this invention to provide a punching apparatus for a converter having a plurality of tuyeres that automatically cleans a tuyre when the rate of flow of blowing air to that particular tuyere falls below a certain predetermined value, independently of conditions at other tuyeres.

A further object of the invention is to provide an automatic tuyere punching unit having a reciprocaoly operated punch rod and a novel and advantageous control device 7 2,696,979 Patented Dec. 14, 1954 responsive to variations in rate of flow of air and operable to initiate operation of the punching unit to cause rapid reciprocation of punch, rod.

It is another object of the invention to provide an advantageous design of an automatic control device for a fluid motor that initiates action of the fluid motor in {esponse to a pressure differential created in an air supply These and other objects of my invention have been attained in a converter having a plurality of tuyeres and a plurality of separate branch air supply lines for blowing air, one branch line leading to each of the tuyeres, by providing a plurality of separate and individual punching units which are mounted on the converter with one unit on and associated with each tuyere. Each punching unit has a punch rod which is connected to the motor for reciprocation of the rod within the tuyere. An automatic control device is mounted upon each of the punching units and includes means responsive to variations in the rate of flow of the blowing air in the branch supply line leading to the associated tuyere. When actuated by a change in the rate of air flow, the automatic control device initiates operation of the fluid motor attached to that particular tuyre.

The automatic control device is itself novel and is adapted to effect initial movement of the motor valve from an exhaust to an admission position. To do this, the control device is provided with a valve shifting member, which is typically and preferably a differential piston subiected at opposite sides to fluid pressure. At one side the fluid pressure is relativelv constant and is preferably the fluid pressure of the working fluid for the motor. The pressure at the other side of the valve shiftin member is varied in order to obtain movement of the valve shifting member. Such variation is obtained by ope ing an exhaust valve, thus connecting one side of the difl erential piston with the atmosphere and causing movement toward that one side. The exhaust valve is actuated bv pressure responsive valve operating means which responds to a differential in pressure created in the air supply line to the tuyere by suitable flow metering means. Such flow metering means is typically a Venturi tube, but other suitable means may be employed. The reduced pressure at the Venturi throat as compared with the static pressure of the air at a point upstream from the Venturi throat establishes a differential pressure which bears a known relation to the rate of flow through the Venturi tube. When the quantity of air. per unit time flowing through the tuyere drops below the quantity deemed satisfactory for converter operation, this pressure differential at the Venturi tube likewise drops below a value which can be predetermined; and this decreased pressure differential in turn acts upon the pressure responsive means for operating the exhaust valve.

Separate means are provided for returning the motor valve from the admission to exhaust position. this valve return means being operated by fluid trapped ahead of the working piston. After return of the motor valve, the exhaust valve of the automatic control device is closed and pressure is again built up at both sides of the differential piston so that the unit is again restored to a condition in which it is ready for operation.

'Other objects, not specifically mentioned, will be brought out hereinafter or will be apparent from the following description of a preferred embodiment of my invention, with reference to the accompanying drawings,

in which:

. Fig l is a rear end elevation of a plurality of automatic punching units mounted on a converter adjacent a plurality of tuyeres, showing a portion of the side of the converter;

Fig. 2 is a side elevation of one of the punching units mounted on the converter, showing means including an adapter housing for mounting the unit on the converter and the connections for supplying air under pressure to the tuyere and to the punching unit and its automatic control means;

Fig. 3 is a fragmentary combined elevation and sectional view on line 33 in Fig. 2, showing a clamp for securing the adapter housing to the converter;

Fig. 4 is a longitudinal median section of a punching unitincluding its automatic control means, and the adjacent tuyere and mounting means, with the punch rod in the retracted or rest position within the tuyere, and with certain parts shown in elevation;

Fig. 5 is an enlarged transverse vertical section on line 55 in Fig. 4;

Fig. 6 is an enlarged longitudinal median section of the punching unit, similar to Fig. 4, with most parts in the same positions as in Fig. 4;

Fig. 7 is a view similar to Fig. 6 but showing the parts in the positions occupied when the punch rod actuating piston is moved to a position near the forward end of its working stroke;

Figs. 8 and 9 are transverse vertical sectional views on lines 8-8 and 9-9 respectively in Fig. 6;

Fig. 10 is a fragmentary longitudinal median section showing the exhaust valve and related parts in the same positions as in Fig. 7, but on a still larger scale;

Fig; 11 is an enlarged transverse vertical section on line 11-11 in Fig. 6;

Fig. 12 is a fragmentary horizontal section on line 12-12 in Fig. 6;

Fig. 13 is an enlarged partial transverse section on line 1313 in Fig. 6; and

Fig. 14 is a fragmentary vertical section on line14-14 in Fig. 6.

Figs. 1, 2 and 4 show a portion of a copper converter A having a plurality of longitudinally spaced tuyeres B arranged in a row along one side thereof. The converter comprises a cylindrical metal shell 1 and a refractory lining 2, and is constructed and mounted for rotation about its longitudinal axis in the conventional manner as shown argd described more fully in Patent 2,432,996 mentioned a ove.

Each tuyere B comprises a pipe or tube 3 extending through aligned openings in the converter shell and the refractory lining into the interior of the converter. The tuyere is a means for introducing blowing air through the walls of the shell and the lining into the body of molten material within the converter.

At the outer end of each tuyere B there is an adapter 4 connected to the outer end of tuyere pipe 3 and secured in place on the converter shell by means of clamp 7 and bolt 8. (See Figs. 2 and 3.) Clamp 7 has a pair of upwardly extending arms 9 which at their upper ends are recessed to engage lugs 11 on the adapter housing, while the lower end of clamp 7 rests against a portion of shell 1. The ends of the clamp are held in engagement with their respective opposing members by tightening down the nut on bolt 8 which passes through the intermediate portion of clamp 7. Adjacent lugs 11 adapter 4 is provided with a convex spherically curved surface portion 12 which is held firmly against a similarly shaped concave seat member 13 by the thrust of clamp 7. The thrust of the adapter holds seat member 13 against the external face of the converter shell.

Adapter 4 has an internal chamber 6 which communicates with the outer end of pipe 3 and forms a part of the passage supplying blowing air to the tuyere pipe. Also connected to adapter 4 and communicating with internal passage 6 is a branch supply line 14 for blowing air. As may be seen from Fig. 1, there are a plurality of tuyres, each with its own punching unit and each provided with its own branch air supply line 14, all of lines 14 communicating at their upper ends with a common manifold or bustle pipe C which extends longitu dinally of the converter.

As shown in Figs. 1 and 4, adapter 4 also serves as a means for mounting in place on a tuyere the punching unit provided for each individual tuyere. Each of these punching units consists generally of a fluid pressure actuated motor F attached to one end of punch rod 15 for effecting rapid reciprocation of the punch rod within pipe 3, as indicated particularly in Fig. 4. Each fluid motor F is provided with an automatic control device indicated generally at G, the control device being mounted directly upon the housing of fluid motor F of the punching unit with which the control device is associated. As will be explained later in greater detail, the automatic control device includes means responsive to variations in the rate of flow of blowing air to the tuyere and operates to initiate action by the associated fluid motor to cause the punch rod 15 within the tuyere to reciprocate and clean out any obstruction which causes air to flow through the pipe at a rate below a predetermined value.

Compressed air, or other suitable elastic fluid, for operating the fluid motor is supplied individually to each automatic control device and punching unit through branch supply line 16; and as may be seen from Fig. l the individual branch lines 16 are connected at their upper ends to a common high pressure manifold 17 which ex' tends longitudinally of the converter.

Referring particularly now to Figs. 4 and 6, it will be seen that fluid motor F comprises cylinder 20 suitably mounted in and between rear cylinder head casting 21 and front cylinder head casting 22. The terms front and rear or other directional terms are used with reference to the working stroke of piston 26 as being in a forward direction, such stroke being from left to right in Fig. 6. The two head castings 21 and 22 are drawn together by a plurality of tie bolts 24, shown in Fig. 2. A fluid tight connection between the walls of cylinder 20 and the surrounding walls of the cylinder-receiving sockets in the two head castings, is obtained by the use of packing means at 25, such as an O-ring type or other suitable type of packing, adapted to hold the relatively high pressures reached in operation of the fluid motor. Within cylinder 20 is working piston 26 which reciprocates within the cylinder and has attached to it piston rod 27 which projects out of the cylinder through an opening in front cylinder head 22. The front cylinder head is provided at 28 with suitable packing, such as an O-ring type seal, adapted to prevent the escape of working fluid under pressure around piston rod 27. At and 28, as well as at numerous other locations, O-rings have been indicated as a preferred means but without necessary limitation to any particular means for holding fluid presures. Any suitable kind of fluid packing may be used at the indicated or other locations as may be required.

Piston rod 27 also extends through and is slidably received in sleeve or gland 30 which supports and guides the piston rod during its reciprocatory movement. Gland 30 is provided with lubrication means in the form of packing at 31 which is provided with a suitable lubricant for the piston rod. Additional lubricant may be supplied to 31 by a suitable conventional type of lubrication fitting, not shown in the drawing.

In order to receive fluid motor F and its automatic control device G for mounting upon the tuyere, adapter 4 is provided at its rear side with cover plate 32. Plate 32 has an opening through which gland 30 extends and also holds between it and the rear face of adapter 4 an apertured ball seat plate 33. Gland 30 extends through the opening in ball seat plate 33, as shown in Figs. 4 and 6. The forward end of piston rod 27 extends beyond gland 30 even when piston 26 is in the rear or rest position of Fig. 4. Thus the forward end of piston rod 27 passes through the internal air passage 6 of adapter 4 and is connected to punch rod 15, the piston rod and punch rod being coaxial of tuyere pipe 3.

In order to prevent the escape of blowing air through adapter cover plate 32 when the fluid motor and its piston rod are removed, adapter 4 is provided with ball check valve 34 which is located inside the adapter inchamber 6. When the piston rod and punch rod are removed from the tuyere, ball 34 falls down by gravity against the central opening in ball seat plate 33 and closes the opening therein to prevent the escape of air. When it is desired to mount the fluid motor in place, the punch rod is inserted in the opening in seat member 33 and when forced ahead moves the ball check out of the way. The movement of the valve ball is guided by a pair of curved guides 35 inside the adapter. In the drawings the ball valve is shown only in the raised position which it occupies when the fluid motor is in place and the punch rod is in the tuyere.

Within rear cylinder head casting 21 and at a position near the rear end of cylinder 24), there is located pressure chest or supply chamber 37. Working fluid under pressure is supplied to chamber 37 through supply line 16 which is connected to communicate directly with supply chamber 37. Near the rear end of cylinder 20, but preferably spaced 2. short distance therefrom, is port 38 which serves not only as a means for admitting working fluid to the rear end of the cylinder behind piston 26 but also as a means for exhausting fluid from that end of the cylinder. As may be seen particularly well from Fig. 7,

lportJgS communicates between cylinder and supply chamer The flow of working fluid from the supply chamber to the cylinder through port 38 is regulated by means of a reciprocable valve assembly that includes slide valve 40 which is within the supply chamber and is movable betweenthe admission position of Fig. 7 and the exhaust position of Fig. 6. When moved forward as'shown in Fig. 7, valve 40 uncoversport 38 and allows direct flow of working fluid from the pressure chest into the working cylinder of the fluid motor F. When the valve is moved to the rear, port 38 is closed to chamber 37 and is placed in communication with port 41 which communicates with the atmosphere thus allowing working fluid in the cylinder to escape through port 38 and the space underneath valve 40 into port 41 and thence to the atmosphere. Adjustable bafile plate 39 is slidably mounted on rear cylinder head casting 21 in position to more or less restrict port 41. and regulate the rate at which fluid exhausts through it. Valve 40 is held against rotation within chamber .37, which is here shown as being circular in f ross-section, by a pair of lateral guides 42, shown in Valve 40 is shifted between the'two operating positions by means of spool 43 which engages the valve and is connected to valve shifting rod 44. Valve rod 44 extends parallel to piston rod 27. Rod 44 and spool 43,- together with the valve member 40 are considered as constituting the valve assembly of the fluid motor for controlling admission of working fluid to the motor cylinder. The rear end of supply chamber 37 is provided with a buffer assembly 45 including a resilient member 45a. Thebuffer assembly limits the rearward travel of the valve assembly to properly locate valve member 40 in the exhaust positron and also absorbs in member 4511 the shock of stopping the valve assembly as it shifts to the rear. The reasons for a sudden reversal and a rapid retraction of the punch rod after a forward punching stroke are set forth 1n greater detail in Patent 2,432,996 referred to above. si rable that pressure actuated valve return means be provided for automatically and positively shifting the valve to exhaust position at a predetermined point in the forward stroke'of punch rod 15. This valve return means compr 1ses aux1l1ary piston 47 mounted for reciprocation in cylindrical bore 48 which is located in the upper portron of front cylinder head 22. The rear end of piston 47 has attached to it piston rod 49which is guided in retamer plate 50 that closes the rear end of cylinder 48 and the forward end of cylinder 58. Piston rod 49 is mounted coaxially with valve rod 44 and the opposed ends of these i wo gods are'adapted to engage each other, as shown in The front end of cylinder 48 ahead of piston 47 is in free communication with the front end of cylinder 20 ahead of piston 26 through passageway 52 so that air trapped 1n the working cylinder ahead of the piston is utilized to actuate auxiliary piston 47, as will be later described more fully. At the rear side of piston 47, cylinder 48 is placed in communication with the, atmosphere by means of passage 53, thus preventing fluid pressure from building up on the back side of piston 47. Piston 47 is provided with an O-ring or other suitable sealing means in order to effect a fluid-tight seal between the p ston and the cylinder walls, and the same is also provided for piston rod 49 in retainerplate' 50. It will be noted that the forward end of piston 47 is provided with a forwardly extending projection so that when the piston In order to accomplish this motion, it is deential bore in cylinder-block 56. The differential bore is in two parts of different diameters; One part is cylinder 57 of relatively smaller diameter which opens at one end to supply chamber 37; the other part is cylinder 58 of relatively larger diameter which is closed at its forward end by retainer plate 50. The walls of the differential bore constrain differential piston 55 to linear movement parallel to valve rod 44, which extends through the differential piston, and parallel to the movement of valve 40. It will be seen that with this arrangement the end of piston 55 of smaller diameter is subjected to the substantially constant fluid pressure existing in supply chamber 37 while the other or opposite side of the piston is subjected to the variable fluid pressure existing in cylinder 58; Cylinders 57 and 58 are in communication with each other through passage 59 which extends longitudinally of the differential piston, the rate of flow of fluid through the passage being closely regulated by-means of orifice screw 60 screwed into the front end of passage 59. Passage 59 is not necessarily in piston 55 but may be located at any other suitable position.

A vent 61 is provided in the wall of the differential cylinder at the junction of the sections of large and small diameters. This prevents air from being trapped in the cylinder underneath the larger diameter portion of piston 55.

Differential piston 55 can slide upon the valve rod 44 in order to permit relative movement between these two members under certain conditions; and disengageable connecting means are provided to connect the piston to valve rod 44 so that under certain other circumstances the two parts move together as a unit. For this purpose, on a forwardly projecting portion of the differential piston there is mounted a plurality of housings 62 which are threaded into the projection of the piston, these housings 62 each being held in place by a locknut 63, as shown particularly in Fig. 11. Within each housing is a compression spring 64 which presses a ball 65 against valve rod 44. The valve rod is provided with a circumferential groove 44a and when balls 65 are pressed into this groove the piston and valve rod are connected together to move as a unit. It will be realized that other types of releasable clutch means may be utilized for connecting the valve to the shifting member. I

Time delay detent means are provided to engage and hold the differential piston against premature movement when the piston is in the rearward or rest position shown in Fig. 6. This detent means is an apparatus of the dashpot type contained in an insert 66 in a vertically extending bore in block 56.

In the bottom portion of the insert is plunger 67 which is providedat its lower end with a projection engageable with annular groove 168 around the circumference of the differential piston. When the plunger engages this groove as shown in Fig.6, piston 55 is in engagement with the forward end wall of the cylinder, passage 52 is not completely closed off by the piston (see Fig. 7).

Except for certain novel features of construction of adapter 4, the apparaus thus far described is generally old and is disclosed in the aforementioned'Patent No. 2,619,938. I have combined with this fluid motor, apparatus of novel design for automatically initiating action of the fluid motor of any individual tuyre whenthe rate of flow of blowing air through the tuyre falls below a predetermined value as measured by the rate of flow in the supply line for that tuyre.

'One element of the automatic control device is a valve shifting member adapted to effect automatically the movement of valve 40 to the admission position. This shifting member is here shown in the form of differential piston 55 which is mounted to reciprocate within a differis held against forward movement. Plunger 67 is normally biased towards the downward position of engagement with the differential piston by spring 68 contained within a bore insidethe plunger. One end of spring 68 presses against the plunger while the other seats against a shoulder in insert 66. Just above this shoulder, is an orificescrew 69 having a longitudinally extending metering orifice. The space below the orifice screw and above plunger 67 is filled with oil which can be forced through the orifice in screw 69 into reservoir space 70 above. Access to reservoir 70 for replenishing or changing the liquid or for other purposesis afforded by removing screw plug 71. Plug 71 has a vent 71a through which any excess pressure in reservoir 70 can bleed off to the atmosphere to prevent accumulation of super-atmospheric pressure in the reservoir that would affect the operation of plunger 67. The upper end of passage 71a is preferably covered by a porous filter to exclude foreign matter. 1

The lower end of plunger 67 is always exposed to the pressure of working fluid in cylinder 57; and this fluid pressure exerts a force on the plunger which raises the plunger in opposition to spring 68. The upward force is greater than the downward force on the plunger when the fluid pressure in cylinder 57 reaches a predetermined value; After this pressure has been reached, plunger 67 rises; but its movement is delayed since the oil below screw 69 must be forced upwardly through the orifice therein into reservoir 70 before the plunger rises Sllfi'. ciently to disengage the differential piston.

In order to prevent plunger 67 from being forced too far down by the-action of biasing spring 68 when the differential piston is not in position to limit downward movement of the plunger, limiting pin 72 is provided as shown in Fig. 8. Pin 72 is threaded into the side of cylinder block 56 and has a portion which projects into a short vertically extending slot 73 in the side of the plunger. At the upper end of this slot is a shoulder which engages pin 72 in order to limit downward range of travel of the plunger.

The release of fluid pressure in chamber 58 ahead of the diflerential piston is through exhaust passage means at the forward side of the differential piston; and fluid flow through the passage means is controlled by an exhaust valve assembly which includes a poppet-type valve 75 which closes against a conical seat at 76 on insert 77 contained in a bore in block 56. The details of this construction are shown particularly in Figs. and 13, the valve being shown in the open position in the first of these figures. In the lower part of insert 77, the stem of valve passes through a bore of substantially larger diameter so that when the valve is spaced from its seat fluid in cylinder 58 can enter into this bore and then into laterally extending passages 78 in the insert. These passages communicate with openings 79 in the cylinder block which lead to the surrounding atmosphere. To eliminate the need for exact alignment of passages 78 and 79, the block is counterbored at 80 to provide an annular manifold passage between the valve insert and the cylinder block which connects all of passages 78 with the terminal passages 79.

The stem of valve 75 extends upwardly through a horizontal wall insert 77 and at its upper end is provided with piston 81 movable within cylinder 82 formed in the upper end of insert 77. Between the bottom wall of the cylinder and the under side of piston 81 is spring. 83 which normally urges the valve upwardly to the raised or closed position of Fig. 13. When closed the valve is also held in that position by pressure of the fluid in cylinder 58 against the head of the valve. In order to open valve 75 against this fluid pressure, piston 81 has a greater area than the area on valve 75 exposed to pressure within cylinder 58. Also, the space under piston 81 is in free communication with the atmosphere through passage 84 (see Fig. 13) which relieves pressure underneath the piston that would interfere with down ward movement of piston 81 to open position. The upper end of cylinder 82 is closed by plate 85 to retain fluid pressure within the cylinder. Thus valve 75 and its piston 81 constitute a differential piston which can be moved to a position in which the valve is open by applying fluid pressure to the larger piston end of the valve, as will now be explained.

Fluid under pressure is admitted into cylinder 82 from cylinder 58 through a devious combination of passages. From cylinder 58, passage 87 leads into the bottom of bore 88 in the valve block. In bore 88 is valve insert 89 which has a centrally located passage 90 through which fluid goes into the interior of the valve insert and then outwardly through radial passages 91 into annular passage 92. This last passage is connected by inclined passage 93 with cylinder 82.

The flow of fluid under pressure from cylinder 58 into cylinder 82 through the system of passages just described is controlled by pilot valve 95 which is mounted for vertical reciprocation in a bore inside insert 89. When in the raised position of Fig. 10, fluid flow through these passages is permitted since passage 90 and radial passages 91 are uncovered by valve 95. When the valve is lowered as in Figs. '6 and 11, the valve closes central passage 90 and covers the inner ends of the radial passages 91 thus preventing any flow of fluid out of cylinder 58. This pilot type of valve structure 95 is selected because passage 90 is of such small diameter that but very little force is required to be exerted upon the valve by the diaphragm to keep it seated against the upper end of passage 90 in opposition to air pressure of the magnitude encountered in cylinder 58, whereas forces of considerable magnitude may be required at times to open or close exhaust valve 75. This way the exhaust valve is opened by the application of air pressure rather than by a direct mechanical connection to the pressure responsive means, now to be described, for operating the exhaust valve, the application of the air pressure being controlled by pilot valve 95 and the pressure sensitive elements.

In order to raise and lower pilot valve 95, it is connected. to the lower end of rod 96 which passes through and is connected toflexible diaphragm 98. As will be explained more fully, this diaphragm is movable in response to fluid pressures applied to it; and a piston or other type of movable member could. be used instead, but a diaphragm is preferred for practical reasons as it can be made more sensitive to pressure differentials of small magnitude. Diaphragm 98 is confined around its periphery by having its marginal portions clamped between opposing shoulders on the two halves of cylinder block 56. Thus the diaphragm subdivides an internal chamber into an upper chamber 99 and a lower chamber 100. Diaphragm. 98 is preferably mounted between a pair of reinforcing members 101 which are relatively rigid. The upper member 101 engages the cylinder block at the top of chamber 99 to limit the upward travel of the diaphragm.

Rod 96 extends upwardly from the diaphragmv and passes loosely through a guide bore at 102 in a web of the cylinder block. A pair of lock nuts 103 on the upper end of rod 96 provides a shoulder against which compression spring 104 bears, the spring surrounding rod 96 and bearing against the block around bore 102.

The upper ends of valve rod 96 and spring 104 are housed in sleeve 105 threaded into the upper portion 56a of the cylinder block. Sleeve 105 has an internal bore which extends the full length of the sleeve and which is closed by a manually operable valve assembly consisting of valve member 106 connected to cap 107 and compression spring. 108 held between cap 107 and the top side of valve seat 109. Valve 106 engages the underside of seat 109 to provide a fluid-tight seal and prevent the escape to the atmosphere of any fluid under pressure in chamber 99 and is biased toward this closed position by spring 108. However, when pressure is manually applied to cap 107, spring 108 is compressed and valve 106 is lowered to open position in which fluid in chamber 99 can escape through bore 102 and around valve 106 to the atmosphere. For this reason, the internal bore of cap 107 is larger than the external diameter of the upper end of sleeve 105. Upon release of manual pressure, the valve is closed by spring 108.

Diaphragm 98 is a pressure sensitive element whose position is determined at any time by the relative fluid pressures existing in upper and lower chambers 99 and 100 respectively. It is desired that the position of the diaphragm be made to respond to fluid pressures existing at some location outside of the automatic control device, in this instance the location being in the air supply line to the tuyere with which the automatic control device is associated. For this purpose, the means for supplying blowing air to the tuyere is provided with a flow meter of the type creating a differential pressure having a known relation to the velocity of air flow within the air supply line. A simple and convenient construction is to form a section of the air supply means in the shape or with the characteristics of a Venturi tube. Equivalent means such as a Pitot tube or orifice meter may be used instead. Obviously this Venturi tube section may be located at another convenient position, but it has been found convenient to form it within adapter 4 as a part of internal cavity 6. Hence adapter 4 is designed so that the blowing air after entering from conduit 14 passes through the constricted throat 110 of the Venturi tube and then into the eglarged portion of chamber 6 before entering tuyere pipe The spaces above and below diaphragm 98 are placed in communication with the air stream at the Venturi tube by means of two separate sets of passages. These are shown in Figs. 6 and 12. From lower chamber 100 passage 112 extends forwardly through valve block 56 to a larger passage 113 in valve block 114. Valve block 114 is fastened to adapter 4 by bolt 111. The forward end of passage 113 is connected to throat 110 of the venturi by way of passage 115 in adapter 4.

By a similar arrangement passage 116 extends from upper space 99 forwardly to passage 117 in valve block 114. From passage 117 communication is through passage 118 to a point within the adapter upstream from the Venturi throat where the cross section of the air supply passage is approximately the same as the cross section within conduit 14. Thus the static pressure existing in the stream of blowing air at any time is communicated to space 99 above diaphragm 98. At the same time the lower fluid pressure existing in Venturi throat 110 by virtue of the increased stream velocity brought about by the decreased cross section of the air passage at the throat, is communicated to chamber 100 beneath diaphragm 98. Hence, the position of the diaphragm is determined by the differential of fluid pressure existing at these two points in the air supply line. 7

As will be further apparent from later discussion, the diaphragm, the pilot valve, and the exhaust valve constitute pressure responsive means for regulating air flow out of the forward cylinder 58 through the exhaust passages closed by valve 75. Because of the types of valves used and the magnitudes of the pressures regulated as well as the regulating pressures on the diaphragm it is preferred to control the exhaust valve indirectly, as through a pilot valve or other actuating means.

In each of bores 113 and 117 there is a valve 120 which is normally urged by compression spring 121 toward a position in which the valve seats against an internal shoulder 114a in valve block 114 to close the associated passage against the escape of air from the air supply line. When the fluid motor F and its control device G are mounted in place on the tuyere, cylinder block 56 engages the ends of valves 120 and presses them inwardly to the position shown in Fig. 12 in which the valves open passages 113 and 117. As long as the control device is in place these valves remain open and the communication between the control device and the air supply line is maintained; and when the control device is removed from the tuyere, bores 113 and 117 are automatically closed to prevent escape of blowing air from the system.

Manually operable means is also provided to release fluid pressure in cl1amber100 at the underside of diaphragm 98 similar to valve 106 and pushbutton 107 already described. Extending laterally from chamber 100 is passage 124 in cylinder block 56. Passage 124 intersects an upwardly extending passage 125 which terminates at its upper end at the bottom of bore 126 in the upper half 56a of the cylinder block. Intobore 126 is screwed sleeve 127 having an internal bore within which valve 128 is mounted. The lower end of valve 128 engages the underside of annular seat 129 in sleeve 127 and the valve is biased toward this closed position by spring 130 mounted on the valve stem and bearing at its lower end against the shoulder on the upper side of valve seat 129. On the upper end of the stem of valve 128 is mounted cap 131 and the upper end of spring 130 bears against the under side of the cap to force the valve upwardly. By manually applied downward pressure on cap 131, spring 130 may be compressed and valve 128 moved downwardly away from the valve seat to permit the flow of fluid out around the valve in the open upper end of sleeve 127. For this reason, clearance is provided between the depending rim of cap 131 and the upper end of sleeve 127.

It is also preferred to incorporate in this structure another feature disclosed in the Patent No. 2,619,938 referred to above. This is the provision of a third air supply system generally designated as back pressure. It consists of an air line 134 connected to some relatively fixed part of each'individual installation, as adapter cover plate 32, all lines 134 receiving air from manifold pipe 133 as shown in Figs. 1 and 2. Air from line 134 goes through passage 135 in adapter plate 32 into valve housing 136 (see Fig. 14) and thence out through the front end of the valve housing and passage 137 into cylinder 48. Within housing 136 is valve 138 normally urged by spring 139 to a closed position; When front cylinder head 22 engages the projecting end of valve 138 as the fluid motor is-mounted on the tuyere, the valve is moved to the open position shown' in- Fig. 6 and air may flow through the passages into cylinder 48. However, when the fluid motor is removed, valve 138 is moved to a closed position by its spring and automatically shuts off the back pressure air supply so that air does not escape to the atmosphere from line 134. This additional air supply is furnished in order to maintain the body of fluid which is trapped in frontof working piston 26 at proper volume and pressure in order to insure full movement of the piston on its return stroke, as will be more fully described. Also, make-up air is furnished to allow for any loss through seepage past either piston 26 or 47. The air or other compressible fluid supplied through line 134 is at a relatively low pressure, say lbs. to 7 lbs. per square inch above atmospheric. This is adequate to insure the necessary body; of com pressible fluid at all times incylinder 20 ahead of working piston 26. Y Y

Another optional feature which is preferably provided in order to check the performance of the automatic control device, is pressure gauge 140. The pressure gauge is connected by means of an upwardly extending passage 141 with the cylinder space 58 ahead of the differential piston and by indicating the fluid pressure existing in this cylinder the pressure gauge readings are evidence of gelrieral operating conditions, as will be explained more Having described the construction of my invention,

I shall now set forth in greater detail the operation of my improved form of automatic control device and how it initiates operation of the fluid motor for reciprocating the punch rod. When the fluid motor F and the control device G are assembled on the tuyere and before operating fluid is applied to the motor, the various parts may be assumed to be in the positions shown in Fig. 6 which are referred to as the normal or rest positions of the several operating parts. Working piston 26 is fully retracted to the rear end of its cylinder. Differential piston 55 is connected to valve rod 44 and both are at the rear of their strokes. The differential piston is held in place by plunger 67. When the assembled'fluid motor and its automatic control device are mounted on adapter 4, connections are automatically made with passages 113 and 117 and the bore in housing 136 as the valves at these locations are automatically opened. Operating fluid, such as compressed air or other elastic fluid, is supplied to the motor and to the control device through conduit 16 which is now connected to supply chamber 37. As typical of the pressures used, but not necessarily limitative thereof, operating fluid is supplied at a pressure in the neighborhood of 75 lbs. to lbs. per square inch with the latter pressure preferred. Compressed air under this high pressure fills supply chamber 37 and cylinder 57, the latter being an extension of the former, and exerts a forward pressure on the end of differential piston 55. Since initially there is no opposing pressure on the other end of the piston in cylinder 58, the piston wouldmove forward if it were not locked in place by detent plunger 67.

High pressure air in rear cylinder 57 flows through passage 59 into forward cylinder 58 at a rate which is determined by the size of the orifice in screw 60; and after the lapse of suflicient time the forward cylinder is completely filled withair at a pressure which is equal to the operating pressure in the rear cylinder and supply chamber 37. When this condition exists the pressure rearwardly on the differential piston is greater than the forward pressure because of the larger area exposed to the air pressure in cylinder 58. During this time the lower end of plunger 67 has been exposed to the high pressure in cylinder 57 and the force on the plunger exerted by the compressed air moves the plunger upwardly, compressing spring 68 and forcing liquid out of the space immediately above the plunger through the orifice in screw 69 into reservoir 70. The orifice in screw 69 is of a selected size to meter the flow of liquid to a desired rate. In this way the time required to lift detent plunger 67 to disengage groove 168 in the differential piston is sufficient that the air pressure in the forward cylinder 58 builds up to a pressure adequate to prevent forward movement of the piston.

Since the detent 67 is responsive to the pressure existing at one side of the differential piston, its operation is automatic. Being of a dash-pot construction it has a delayed action that prevents premature release of piston 55. Forward motion of the piston is thus delayed until the normal desired fluid pressure is built up in the forward cylinder so that the forward end of the piston is subjected to fluid pressure adequate to hold it in the rest position without the operation of detent plunger 67. This action is of value when the assembly consisting of a fluid motor and its control device is first mounted on the tuyere as when a unit is being replaced that has been removed for servicing. Furthermore, by controlling the strength of spring 68 the detent can be prevented from disengaging the difierential piston when the operating air pressure in the supply chamber falls below a predetermirliled minimum value, as for example 75 lbs. per square 111C t Following initial assembly, air also enters through passage 137 from' the back pressure line 134 which supassignm- 11 tively with compressed air at this low pressure, though the invention is not limited thereto.

When the various cylinders within the fluid motor and its attached control device have become charged with fluid under pressure and pressures are stabilized throughout, the device may be said to be cocked since it is now ready for normal operation. All parts are still in the same position as in Fig. 6, except that detent plunger 67 is raised clear of the cylinder as shown in Fig. 7. The device will now operate automatically in response to pressure conditions existing at the Venturi tube through which blowing air is supplied to the tuyere pipe. Blowing air is normally supplied through conduit 14 to pipe 3 at a pressure of approximately 12 to 15 lbs. per square inch, although this pressure is in no way limitative upon the present invention. When the tuyere is unobstructed blowing air flows through it and Venturi throat 110 at a known rate depending on the supply pressure; and as a result there is a known differential between the pressures existing in Venturi throat 110 and at a selected point upstream from the throat where the air passage has its full normal cross-sectional area.

it will be understood without detailed explanation that as accretions forms at the forward end of the tuyre the tuyere becomes artificially constricted with the result that air flows through it at a lower rate than normal. In consequence there is a decrease in the rate of air flow through the Venturi section and a new and lesser differential is established between the air pressures existing in the Venturi throat and at the same selected point upstream therefrom. The two points at which these measurements are taken are of course fixed and are the locations at which passages 115 and 118 open into the Venturi tube. The control device is designed to operate the fluid motor when the diiferential in pressures existing between these two points drops to or below a predetermined value.

By means of passages 112, 113 and 115 the fluid pressure existing at the Venturi throat is also maintained in space 100 beneath the diaphragm'98; while by means of passages 116, 117 and 118 the higher pressure existing upstream from the Venturi throat is applied to space 99 above the diaphragm. Under normal flow conditions the differential in pressure is sufficient and in a direction to deflect diaphragm 98 downwardly until valve 95 closes ports 90 and 91, thus preventing escape of fluidunderpressure from cylinder 58 ahead of the differential piston. Downward movement of diaphragm 98 compresses spring 104. When the rate of fluid flow through the Venturi throat drops below the minimum established for satisfactory converter operation, the differential fluid pressure on diaphragm 98 is reduced to a predetermined value. At or below this predetermined value, the upward force of spring 104 overcomes the net downward force on the diaphragm as a result of the fluid pressures applied there to and spring 104 lifts the diaphragm upwardly, carrying valve 95 upwardly to the position of Fig. 10 in which air passages 90 and 91 are open.

With these latter passages open, compressed air can escape from cylinder 58 through passages 87, 90, 91, 92 and 93 into cylinder 82. In this cylinder the fluid pressure builds up rapidly until piston 81 is driven downwardly, as shown in Fig. 10, compressing spring 83 and moving exhaust valve 75 to the open position. The quantity of air escaping from cylinder 58 through these passages into the cylinder 82 is relatively small, since the volume of cylinder 82 is small compared with the volume of cylinder 58. As a result there is no appreciable reduction in the value of the air pressure in cylinder 58 and cylinder 82 fills very rapidly. With the opening of exhaust valve 75 an escape passage to atmosphere of comparatively large size is made available through passages 78, 80 and 79 to cause a sudden and substantial drop in pressure in cylinder 58.

This drop in pressure permits differential piston 55 to move forwardly under the force applied to it by the operating air pressure at the rear of the piston. As the piston moves forward it gains in velocity and the forward cylinder continues to exhaust through open valve 75 so that the forward motion of the piston is not hindered.

As the differential piston moves forward it carries with it rod 44 by virtue of its connection thereto through balls 65 engaging circumferential groove 44a of the rod. This moves valve 40 from the exhaust position of Fig. 6 to the admission position of Fig. 7 in which inlet port 1 s uncovered by the valve. This establishes free communication between supply chamber 37 and cylinder 20.

Forward movement of valve rod 44 also moves piston 47 and piston rod 49 by virtue of engagement of the latter with valve rod 44. This forward movement continues until piston 47 hits the front end wall of cylinder 48 as in Fig. 7, thus stopping forward movement of rods 44 and 49. The parts are preferably proportioned so that the differential cylinder also engages retainer 50.

The back pressure on the forward side of piston 26 is sufficient to keep the working piston normally in a fully retracted position (as in Fig. 6) in which the piston covers inlet port 38. However, this does not prevent admission of working fluid into the cylinder since the piston has small but adequate clearance between it and the cylinder walls to allow high pressure fluid to pass from inlet port 38 around the piston to reach the rear face of the piston and drive it forward. For this reason. packing as shown at 26a to effect a fluid-tight connection betwen the piston and cylinder walls is limited to the forward end of the piston at a position which is always forward of inlet port 38. Two advantages are secured by keeping the piston when at rest at the extreme rear end of the cylinder. In the first place, the piston always makes a full and uniform stroke since it is definitely positioned at the beginning of each working stroke. In the second place, the partial constriction of port 38 causes fluid pressure behind the piston to build up more slowly than if the space were at once fully opened to the port with the result that piston 26 accelerates more gradually and more smoothly.

After slide valve 46 has been advanced to uncover at least a part of port 38, the operation of the fluid motor F is initiated and its operation is then substantially as described in greater detail in the Patent No. 2,619,938 referred to above. Briefly stated, the piston starts to move with a fluid pressure of relatively nominal value, perhaps 5 to 7 lbs. per square inch, ahead of it and a relatively high working pressure reaching perhaps to 109 lbs. per square inch behind it. This relatively greater force causes the piston to accelerate rapidly, reaching a maximum velocity at about midpoint of the forward stroke. For about the last 15% of the stroke, the piston decelerates rapidly because of the absorption of its kinetic energy by air trapped between the piston and the forward end wall of the cylinder. The body of fluid ahead of the piston eventually absorbs all of its energy remaining after the punch rod removes accretions in the tuyere and brings the piston to a stop at the dotted position of Fig. 4, and then by expanding returns the piston rapidly to the rear end of the cylinder. The energy of forward movement is sufficient to raise the pressure ahead of the piston to several hundred pounds per square inch, which pressure insures full return of the piston.

This return action is permitted by virtue of the valve return means which shifts the slide valve 40 to exhaust position at some point late in the forward stroke of the working piston, which is about the position of the piston in Fig. 7. As the pressure of the fluid ahead of the working piston builds up the same pressure is transmitted through passage 52 to piston 47, and a point is reached at which the pressure acting upon piston 47 becomes sufficient to force that piston rearwardly in cylinder 48. Because of engagement of piston rod 49 with valve rod 44 the rearward movement of the piston shifts the valve rearward to the exhaust position of Fig. 6. In so doing, rod 44 is disconnected from differential piston 55 since the differential piston is held in its forward position by the continued high operating pressure on its rear side. Thus the slide valve is returned alone to its initial position in which port 38 is connected through the. valve with exhaust port 41.

As piston 26 starts its return or rearward stroke under the relatively higher fluid pressure existing on its front face, working fluid is exhausted through port 41 at a rate which can be controlled by positioning slide 39 so as to restrict more or less the net opening of port 41, to the atmosphere. This rate of exhaust has an effect upon the piston movement. The more the exhaust outlet is restricted, the greater the resistance to the piston during its return movement; and this may be utilized to slow down its rearward velocity. As the leading face of the piston passes port 38, a small amount of fluid is trapped between it and the rear cylinder head to provide a cushion pressure that rapidly decelerates the piston. However, in actual operation the piston may strike the end ofthe control device.

spasms wall-and this, combined with the elastic nature of the trapped air, causes the piston to rebound silghtly'beyond port 38. The piston thus mzy bounce or oscillate before it comes to rest. The final rest position is at the end of the cylinder (as in Fig. 6) since the pressure between the piston and the rear end of the cylinder is reduced to zero while at the forward face of the piston there is always the residual back pressure which pushes the piston rearwardly in its cylinder. 1

-- Assuming that the punching stroke of rod 15 is suflicientto clean out the accretions in the tuyere, normal flow conditions are reestablished which in turn causes 'reestablishment of the normal pressure differential across diaphragm 98. As a result the diaphragm is again de- -fiected downwardly by air pressures acting on it, valve 95 cuts E escape of fluid under pressure from cylinder 58 through passage 87 and consequently pressure can now build up in cylinder 58. Air under pressure continually flows through passage 59 into cylinder 58 but during this time has notbuilt up any pressure in the chamber as long as exhaust valve 75 remains open In practice, the reduction-of pressure in cylinder 58 to substantially atmospheric allows the air under high pressure to escape from cylinder 82, which air has caused exhaustvalve 75 to open. In this way cylinder 82 is drained of air, permitting the exhaust valve to close and again retain pressure within cylinder 58 in front of the differential piston.

- With the restoration of high pressure in cylinder 58, the force on the forward face of piston 55 is greaterthan on the rear face and the piston is again driven back to its rearward position shown in Fig. 6 when balls 65 snap into groove 44a and again connect the piston to the valve.

The fluid motor and its control device are again-cocked and ready for another stroke.

The sizes of the various air'passages are such that it may require several seconds to ready the apparatus for another stroke. A normal operating condition is indicated by a pressure gauge reading of 100 pounds, or whatever the line pressure is in conduit 16, within an interval of 10 to seconds depending on the size of the orifice in-screw 60, following the forward stroke of the piston. If a much lower gauge reading is indicated, it is a warning to the operator that for some reason the device is not operating properly.

It is characteristic of this fluid motor that piston 26 -moves through a singlecomplete reciprocation forward and back for each opening of motor valve 40, which is promptly closed and cannot again be opened for at least several seconds even when everything is working properly. Several features contribute to this, such as the small size of the orifice in screw 60, the disconnectable nature "of the connection of piston 55 to valve rod 44, and others. "For this reason, the fluid motor is termed a single-cycle motor to distinguish from one adapted to repeated cycles or tocontinuous application of operating pressures to piston 26.

A number of different reasons may cause malfunction For example, dirt my clog one of the small air passages or settle on a valve seat, and prevent the valve from properly closing. Under such conditions air pressure in cylinder 58 may not build up to the minimum operating pressure, herein assumed to be 75 pounds per square inch.

It sometimes happens that the punch rod does not sufliciently clean out a tuyere.

This may be a result of excessive accretions in the tuyere but is more likely a result of mechanical failure because .the tip of the punch rod is worn or broken or may perhaps have been melted ofi. Under these circumstances, the normal rate of air flow through the tuyere is not refor one of the reasons enumerated, or some otherreason,

the punching unitis not operating properly. If the difli- :culty. is in the. failure of the punch rod to enlarge the .tuyere sufiiciently, this maybe ascertained quickly by .cocking and subsequently actuating the punching unit by means of'the manual control buttons. I

differential piston.

The motor and control mechanism may be chocked manually by depressing button 131 which opens valve 128 and places the under side of diaphragm 98 in com.- munication with the atmosphere. As a result the pressure underneath the diaphragm is lowered and the air pressure above the diaphragm forces valve downwardly to a closed position. If the button is held down until gauge shows a pressure equal to the pressure of line 16, then the operator knows that the differential piston has again been connected to the valve rod and the device is cocked ready to operate. Action of fluid motor F may now be initiated by releasing button 131 since upon release the diaphragm is raised by spring 104 in the absence of air pressure above the diaphragm sufficient to hold it down in position to close valve 95.

The control device may be manually operated to initiate a stroke of the working piston at any time under normal operating conditions by manually depressing button 107. When button 107 is depressed sufiiciently to unseat valve 106, the space above diaphragm 98 is vented to the atmosphere and the higher pressure beneath the diaphragm raises pilot valve 95, initiating action of the fluid motor in the manner described above.

During such periods as the blowing air may be shut off so that there is no pressure above atmospheric in conduit 14 or adapter 4, thedevice may still be operated manually by depressing button 107 as far as possible. When no differential air pressure is applied to the diaphragm it is raised by spring 104 to the upper position of Fig. 10 in which pilot valve 95 is open. As valve 106 moves down, it first engages the upper end of valve rod 96, and further downward movement of the button causes valve 95 to move downwardly to a seated or closed position. The valve is held in this position by maintaining manual pressure on button 107 until line pressure, as indicated by gauge 140, has been built up in cylinder 58 ahead of the When button 107 is now released, spring 104 raises the diaphragm and valve 95 with the result that action of the fluid motor is initiated in the manner previously described.

From' the foregoing description it will be seen that various changes in details and arrangement of parts will occur to persons skilled in the art without departing from the spirit and scope of my invention. In the course of k the description, various departures from the preferred design have been mentioned but it will be realized that these are notthe only changes that may be made; and it is to be understood that I am not necessarily limited to the exact details of the disclosure already made. Consequently, it is to be understood that the foregoingdisclosure is considered as being illustrative of, rather than limitative upon, the appended claims.

I claim:

1. The combination with a converter tuyere subject to accumulation of obstructions during normal converter operat on, a punch rod reciprocable within the tuyre for perio dlcally removing such obstructions, and an air supply line connected to the tuyre for supplying blowing air that flows past the zone of obstructions into the converter, of apparatus for automatically reciprocating the punch rod when obstructions reduce air flow through the tuyere below a predetermined value, comprising: a single cycle fluid motor operatively connected to the punch rod to rec1proca-te the rod upon supply of operating fluid to said motor and having a valve movable from a normal rest position shutting off supply of operating fluid to the motor to a second position admitting operating fluid to the motor; a movable valve shifting member; means for subjecting opposite sidesof said valve shifting member to fluidpressure; exhaust passage means at one side of the valve shifting member opening to the atmosphere for relieving fluid pressure at said one side to produce movement of the valve shifting member; means connecting the valve to the valve shifting member to move the valve to said second position in response to said movement of the valve shifting member; exhaust valve means normally closing said exhaust passage; fluid pressure responsive means for opening said exhaust valve; and passage means placing the pressure responsive means in communication with the blowing air supply line to actuate said pressure responsive means when the rate of flow in the tuyere past the obstructions drops below a predetermined value.

.2. The combination as in claim 1 in which the ,apparatus for reciprocating the punch rod also CO11 '1PI1SS a second fluid supply .line supplying operating .fluid to the motor and directly to the valve shifting member at the side of the shifting .member away from the exhaust :p-assagemeans; and constricted passage means communicating with the spaces at each of the two sides of the valve shifting member-conducting operating fluid to said one side of the shifting member adjacent the exhaust means at a relatively slow rate.

.3. The combination as in claim 1 in which the fluid pressure responsive means for opening the exhaust valve includes means biasing the exhaust valve toward a normally closed position; a piston connected to the valve; fluid passage means leading from said one side :of the valve shifting member to one side of said valve piston to apply fluid pressure to the piston in a direction to open the exhaust valve; a pilot valve controlling fluid flow through the last named fluid passage means; and a movable :pressure sensitive element connected to the pilot valve and sensitive to fluid pressure in the blowing air supply line to hold the pilot valve normally in closed position and to move the pilot valve to open position when the flow of blowing air drops below a predetermined value.

4. The combination as in claim 3 that also includes manually operated means for moving the pilot valve to closed position.

5. The combination as in claim 3 that also includes fluid passage means communicating between one side of the pressure sensitive element and the atmosphere, and a valve normally closing the last mentioned fluid passage and movable to open the passage to release fluid pressure acting on one side of the pressure sensitive element.

6. In combination with a converter tuyre and a blowing air supply line leading to the tuyere, an apparatus for automatically punching said tuyere comprising: a punch rod mounted for reciprocatory movement in the tuyere; a fluid motor for effecting a single, rapid reciprocation of the punch rod upon supply of Operating fluid to said motor; a valve normally held in a rest position shutting ofl supply of operating fluid to said motor and movable to a second position to supply operating fluid to said motor; a cylinder; a differential piston reciprocable in said cylinder; means for subjecting the piston at the side of smaller area to a relatively constant operating fluid pressure; means for supplying fluid under pressure to the opposite side of said piston to hold the piston in a normal rest position; exhaust passage means leading from said cylinder at said opposite side of the piston for releasing fluid from said cylinder to reduce the pressure at said opposite side; means operatively connecting the piston to said valve to shift the valve from said rest position to said second position in response to such decrease in pressure at said opposite side of the differential piston; exhaust valve means normally closing said exhaust passage; and means communicating with said air supply line and responsive to variations in flow of fluid in said air supply line, operable to open said exhaust valve when the rate of flow of fluid in said air supply line decreases below a predetermined value.

7. The combination as in claim 6 in which the apparatus for punching the tuyere also comprises: detent means biased toward a position of engagement with the differential piston when in normal rest position, said detent means being subjected to the relatively constant pressure at the smaller side of the differential piston to be held out of engagement with the piston when said pressure exceeds a predetermined value; a constricted passage through the piston conducting working fluid from the side of smaller area to the other side of a relatively slow rate; and time delay means associated with the detent means to delay disengagement from the piston until fluid pressures at both sides of the diflerential piston are substantially equal.

8. In an automatic control device of the character described for controlling actuation of a single-cycle fluid motor having a reciprocable valve shiftable between a normal rest position shutting off supply of operating fluid to the motor and a second position admitting operating fluid to the motor, the combination comprising: a cylinder; a differential piston reciprocable insaid cyltinder; means for subjecting the piston at the side of smaller area to a relatively constant working fluid pres sure; a .constricted passage for supplying fluid under pressure at a relatively slow rate to the opposite side of said piston to hold the piston in a normal rest position; detent means biased toward a position of engagement with the difierential piston when in said normal rest position, said detent means being subjected to the relatively constant fluid pressure at the smaller side of the differential piston to be held out of engagement with the piston when .said constant pressure exceeds a predetermined value; exhaust passage means leading from said cylinder at said opposite .side of the piston for releasing fluid from said cylinder to reduce the pressure at .said opposite side; means operatively connecting the piston to said valve to shift the valve from said rest position to said second position in response to such decrease in pressure at said opposite side of the piston; an exhaust valve normally closing said exhaust passage; and pressure responsive means connected to an air supplyline outside the control device and responsive to variations in flow of fluid in said line, operable to open said exhaust valve when the rate of flow of fluid in said air supply line decreases below a predetermined value.

9. An automatic control device as in claim 8 that also includes time-delay means associated with the detent means to delay disengagement from the piston for suflicient time that fluid pressures at both sides of the difierential piston are substantially equal.

10. In an automatic control device of the character described for controlling actuation of a fluid motor having a valve shiftable between exhaust and admission positions, thecombination comprising: a movable valve shifting member operatively connected to the motor valve; means for subjecting opposite sides of the valve shifting member to fluid pressure; exhaust passage means at one side of the valve shifting member for relieving fluid pressure at said one side; exhaust valve means regulating fluid flow in the exhaust passage; a Venturi tube through which a stream of air flows; pressure responsive valve operating means opening said exhaust valve means in response to fluid pressure existing at said Venturi tube and comprising a second movable member, means for subjecting one side of the second movable member to the fluid pressure existing in the throat of the Venturi tube, and means for subjecting the opposite side of the second movable member to the fluid pressure existing at a point upstream from the Venturi throat; and valve means normally biased to a closed position and manually operable to move to an open position to release fluid pressure acting on one of the two opposite sides of the second movable member.

11. In an automatic control device of the character described for controlling actuation of a fluid motor having a valve shiftable between exhaust and admission positions, the combination comprising: a movable valve shifting member operatively connected to the motor valve; means for subjecting oppositesides of the valve shifting member to fluid pressure; exhaust passage means at one side of the valve shifting member for relieving fluid pressure at said one side; exhaust valve means regulating fluid flow .in the exhaust passage; pressure responsive valve operating means opening saidexhaust valve means in response :to'fluid pressure existing at a location outside the control device, and valve means normally biased toward a closed position and manually operable to move to an open position to release fluidpressure acting upon said pressure responsive valve operating means independently of pressures existing .at said location outside the control device.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 425,202 Blanchard Apr. 8, 1890 813,209 Holmes Feb. 20, 1906 1,257,369 Lower Feb. 26, 1919 1,423,786 Zoelly et a1. July 25, 1922 1,797,297 Ringle Mar. 24, 1931 1,907,538 Hanna May 9, 1933 1,980,349 Neveu Nov. 13, 1934 2,020,847 'Miterefi Nov. 12, 1935 (Other references ,on following page) Number UNITED STATES PATENTS Name Date Burke June 8, 1937 OConner Aug. 9, 1938 5 Ganahl et a1. Nov. 28, 1939 Phillips June 3, 1941 Doerner July 10, 1945 Number Number Name Date Larson et a1. Dec. 23, 1947 Hunter Oct. 12, 1948 FOREIGN PATENTS Country Date Great Britain June 18, 1943 Germany June 14, 1937

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